If you are considering building a pergola that butts against the fascia of your home and would be roofed in, do not and we stress, do not pitch the roof towards the house for the roof to evacuate to the homes existing guttering, this would be a big mistake.

The area between the pergola and house guttering is notorious for leaking when the roof falls to the guttering and can also be notorious for leaking when the roof falls away from the house due to the fact that this area may have guttering that falls wrong and holds water.

If the previous is so I suggest that at a minimum the guttering in this area to be realigned to fall properly to the downpipes and an L shaped cap flashing be installed 100mil over the roofing and 50mil into the guttering, this would be the least that we would do. This would hold you in good stead for most rain however in a deluge it is still possible to incur leakage in this area.

Better still or should I say the best job to make good a pergola roof to the home to alleviate any possibility of rain ingress, is to install an apron flashing over the pergola roof and up under the roof covering of the home. The rain water will then evacuate from the house roof over the pergola, this is the best way to weatherproof this area.

However if you have inherited a roofed in pergola where the guttering is holding water from the previous owner, this is what I suggest you do –

For a tiled roof – you will need to remove the bottom course of tiles and push up the second course, fix an apron flashing at least 250mil over the pergola roof and guttering and for the flashing to continue up half way above the second course, fix it to the pergola roof with screws and to the tile batten that is exposed, weather either end of flashing, stop end gutter so no water can enter and pull down second course to completion as depicted in image.

pergola guttering

Apron flashing making good between tile roof and pergola roof also showing how flashing is weathered either end with turn up to the right and tile flashed to the left with a diverter either end to spread water

For a colorbond roof – do as for a tiled roof, however you will need to remove the bottom row of screws to allow the flashing to go up under the roof sheet. The apron flashing is the most professional way to weather a low pitched roof to the home.

We hope this information is of use to you we like to pass on our knowledge from our 50 years in the roofing industry.